The present invention relates to a method of manufacturing a semiconductor device, which can be used appropriately as, e.g., a method of manufacturing a semiconductor device having a nonvolatile memory.
As an electrically writable/erasable nonvolatile semiconductor storage device, an EEPROM (Electrically Erasable and Programmable Read Only Memory) has been used widely. Such a storage device represented by a flash memory which is currently used widely has a conductive floating gate electrode or a trapping insulating film surrounded by oxide films under the gate electrode of a MISFET. A charge storage state in the floating gate or trapping insulating film is used as stored information and read as the threshold of the transistor. The trapping insulating film refers to an insulating film capable of storing charges therein, and examples thereof include a silicon nitride film. By injection/release of charges into/from such a charge storage region, the threshold of the MISFET (Metal Insulator Semiconductor Field Effect Transistor) is shifted to allow the MISFET to operate as a storage element. The use of a trapping insulating film such as a silicon nitride film as a charge storage region provides advantages over the use of a conductive floating gate film as the charge storage region such that, due to discrete storage of charges, data retention reliability is high, and the high data retention reliability allows the oxide films over and under the silicon nitride film to be thinned and allows a voltage for a write/erase operation to be reduced.
Japanese Unexamined Patent Publication No. 2004-200504 (Patent Document 1) describes a technique related to a semiconductor device having a nonvolatile storage element.